“Points up a real problem: barrel of a firearm really wants to be made of hardened steel. "As cast" metal is a poor second best; plastic is OK for a single shot "scare all the liberals" toy gun, but not much more.
Gotta believe that the SLA pistols that have been posted on the Web recently are likely to be more dangerous to their wielders than to their targets. Think there's a good reason that all the videos of these gadgets show them being fired using a lanyard tied to their triggers!”
“Well, if a DMLS machine isn't in your budget, can always use investment casting to make metal parts via 3D printing. Just make a (slightly outsized) plastic part with a 3D printer, pack it in clay, fire it into bisque (evaporating the plastic), and, voila, you have a 3D female mold, ready to pour molten metal into. The fired ceramic makes a "one shot" mold; you have to destroy the mold to release the cast part. But, does work. Jewelers have been making cast parts this way since Egyptian times.
Easier to do with low melting point alloys like brass, pewter, gold, or silver, but, can be used for steel, if you have access to a furnace that will melt steel...”
Robert Williams2 on Nov 8, 2013 at 14:34:46
“In fact, many early cannons were mad using this process, by bell makers.
And, well, they exploded quite regularly.”
Croaxleigh on Nov 8, 2013 at 14:18:57
“Not all plastics are created equal, though. PLA is preferable to ABS or other types of plastic for this sort of thing, since it melts easily without releasing potentially dangerous vapors. It works essentially like lost wax casting, except the PLA melts out instead of the wax.”
“Did get dunked in the Charles River once, circa 1970, whilst learning to sail. Kinda smelly, but, didn't take any harm.
Biggest problem the river had back then, maybe still, is that the bottom of the basin is full of salt water, tidal back flow from Boston Harbor. The salt water is denser than the fresh water above it, so, the basin remains stratified.
Without any vertical circulation, the salt water at the bottom of the basin has become anaerobic, and supports a good sized population of anaerobic microbes, which produce stinky "marsh gas" by the thousands of cubic meters. A disincentive to swimming...”
“NH House of Representatives has at least one member form every town and village in the State; some towns with as few as a half dozen or so voters send Reps to Concord. As a result, NH House is the 3rd largest legislative body in the world, and has a fair number of true "zoo specimens" in its ranks.
Also, should note that there are a few (small) towns in NH whose politics are dominated by local "splinter" religious and political groups. Perhaps no accident that the Libertarians decided a few years back that NH was their best best to establish a Randite, Laissez Faire paradise hefre in th US.”
“Very interesting. Had once concluded that having more than 2 sexes was maladaptive on mathematical grounds. Argument is that a pair of individuals from a 2 sex species meeting each other have a 1/2 chance of being able to breed. 3 individuals from a 3 sex species meeting each other have only a 6/27 chance of being a breeding trio. Probability of successful mating 2X worse than that for 2 sex species, and the odds get worse as the number of sexes goes up.
Appears that pairs of this particular 7 sex micro-organism can mate as long as the two individuals are not the same sex. Probability of successful mating would then be 42/49, better than that of 2 sex species...”
NotAfraidmm on Mar 28, 2013 at 15:38:34
“so no same sex mating is allowed with a "7 sexed" organism?
"Because the mating type gene helps Tetrahymena recognize others of a different sex, the researchers say that the finding could shed light on how other cells, including those in humans, recognize those that are different from themselves."”
“Needs to be done carefully; steel is prone to failure when exposed to hydrogen under pressure. This was discovered early in the last century, when the Faber Werks in Germany was developing the Haber-Bosch process for producing artificial nitrates. The pressure vessel in a Haber-Bosch plant carries nitrogen and hydrogen, at high temperature and pressure (~ 200 bar, ~ 500C); several of the early pressure chamber designs failed catastrophically...”
“BS. "What is allowed" is neither a subset nor a superset of "What did you do." Try drawing a Venn diagram...”
jhnnxn on Feb 15, 2013 at 18:02:37
“You assume that they do things that they're not allowed to do. If that was the case your math would be correct. However they're not breaking laws, they're getting laws made to order. Huge difference, therefore you fail math today.”
“Your example is one of categories, and how they do and don't overlap: set of all squares is a (proper) subset of the set of all rectangles. Not applicable: neither Warren's actual question or the one than Curry answered belong to categories that overlap much at all; they are largely disjoint. Which, of course, is why Curry chose to answer a different question than the one actually asked.
Equivalent would be a child, replying to Mom's query as to whether he raided the cookie jar, saying "I don't really like Oreos..."”
jhnnxn on Feb 15, 2013 at 08:50:57
“Wrong. The answer to her question was logically a subset contained within the her reply. Her ignorance,or for that matter yours, in seeing this doesn't change it.”
“Let's see if I can explain this to you so that you can understand:
Liz asked the question: "When did you last prosecute anyone?"
Curry answered a different question: "Are you legally required to prosecute anyone?"
There, isn't that simpler?”
jhnnxn on Feb 15, 2013 at 08:14:53
“I can understand your desire for simplicity for all. Equal footing and all. Let me give you something to ponder. Every square is a rectangle, but not every rectangle is a square. Apply that to the situation at hand and get back to me.”
Seriously, though, if the GOP can place the likes of Aiken and Broune... on the House Committee on Space, Science, and Technology(?!?!?), can you blame me if I find it comical that a self described conservative can use the term "crackpot" to describe Democrats?”
“I suspect that there has been a bit of a leap to reach the conclusion that the particular vertebrate animal, Pikaia (of Burgess Shale fame), was the exact organism that hosted this genetic change. Comparative genetics would readily allow an approximate dating of when the glutamate gene was duplicated in the vertebrate genome, and, at 550 MYA, Pikaia is one of the few known vertebrate organisms from the fossil record. Still, duplication could as readily have occurred in one of the Conodont critters that were roughly contemporous with Pikaia, or, could have occurred in a primitive vertebrate of which we have no fossil record.
Needles to say, the Burgess Shale fossils of Pikaia did not preserve the animal's DNA...”
ythri on Dec 6, 2012 at 14:28:35
“I don't think it's helpful when they point to a specific fossil animal and say that is was the one where a genetic event occurred. They should just say it was an animal like Pikaia, from the same time period.”
“One major reason that modern thinkers have "giant's shoulders" to stand on... is that our modern society is literate. A paleolithic inventor who discovered a more elegant way to snare rabbits would have had only indifferent success in having his new idea promulgated, even to the next generation of his or her own tribe.
With the invention of writing, ideas could spread further and faster. Notably, the scientific and technical revolution that continues to fuel our own civilization really began in earnest with Gutenburg's printing press, which allowed for even faster and more widespread dissemination of knowledge.